Switching power or dynamic power consumed by digital circuits is generally governed by the formula. P=FCV^2, wherein C is the value of the capacitance being switched, F is the clock frequency of switching, and V is the magnitude of the voltage occurring at the switching component. There is a well recognized need in the art, especially with respect to handheld and battery operated devices, for reduced power consumption. Conventional techniques to reduce power consumption involve lowering the voltage V and the frequency F in order to reduce dynamic power.
Digital circuits are usually integrated on semiconductor dies, wherein several functional blocks may be present on a single semiconductor die. These functional blocks may encompass a wide variety of functional elements, and thus, their frequency and voltage needs may vastly differ. Therefore, in order to meet low power targets, each of these functional blocks may be independently operated such that their respective frequency and voltage values may be appropriately scaled.
However, operating the several functional blocks independently at individual voltages and frequencies may require individual clock and voltage sources for each functional block. In general, because voltage sources essentially control the power supply, voltage sources will also be referred to as power sources in this description. Accompanying challenges arise in providing such individual power sources. With reference now to FIG. 1, a conventional digital circuit 100 with N functional blocks: 1021 . . . 102N is illustrated. Digital circuit 100 may be integrated on a semiconductor die, wherein the semiconductor die may be integrated in a package with a limited number of pins to connect the package to a next level of assembly, such as a printed circuit card. The pins may include signal input/output pins as well as power pins. The printed circuit card may itself be limited in the number of pins it can accommodate.
Returning now to FIG. 1, power sources 1041 . . . 104N may be coupled to digital circuit 100 in order to supply individually tailored power to functional blocks 1021 . . . 102N respectively. Power sources 1041 . . . 104N may be configured for frequency and voltage scaling, such that customized clocks and voltages may be provided to each of functional blocks 1021 . . . 102N. As shown, power sources 1041 . . . 104N may be provided outside the semiconductor die or package which houses digital circuit 100. Due to the limitations in resources (e.g. pins), and high costs associated with providing a large number of power sources as the number of functional blocks increase, conventional implementations such as digital circuit 100 become impractical.
Alternately, known implementations may include on-die voltage regulators (e.g. for regulating frequency or voltage, or collectively, “power”) that are integrated on the same semiconductor die as the functional blocks. While conventional on-die voltage regulators may be configured to provide, for example, programmable supply voltage to individual functional blocks, they come at prohibitively high costs. These on-die voltage regulators usually consume a large on-die area. The on-die voltage regulator of choice is a switch mode power supply topology, which may include inductors. The use of a number of inductors in order to deliver power to the individual functional blocks increases costs, and moreover, these inductors are not easily amenable for integration on the semiconductor die. Further, these on-die voltage regulators generate significant amounts of thermal energy which is undesirable in mobile devices.
Accordingly, there is a need in the art to overcome aforementioned limitations of conventional implementations, and deliver fine-grained power management solutions for digital circuit designs comprising various functional blocks integrated on a semiconductor die.